I'd like a function that blocks until data is available on one of two channels and then returns that data wrapped in an Either. Here is my naive implementation: readEitherChan::Chan a -> Chan b -> Either a b readEitherChan a b = do var <- newEmptyMVar forkIO (readChan a >>= putMVar var . Left) forkIO (readChan b >>= putMVar var . Right) val <- readMVar return val eitherChan a b left right = readEitherChan a b >>= either left right But creating an MVar and starting two threads feels like a lot of overhead for a simple operation. Is there a better way or is forkIO so efficient that I shouldn't care? -Alex- _________________________________________________________________ S. Alexander Jacobson mailto:me@alexjacobson.com tel:917-770-6565 http://alexjacobson.com